Do plants sense their environment? changes in essential resources herbivory/disturbance external stimulus If so, what do they do about it? do plants process information?
Primary and secondary growth allow trees to be giants Are their limitations to plant height? Redwoods = 116 m What resource most limits growth?
Large trees move hundreds of gallons of water a day only small amounts needed for growth/photosynthesis Gravity harder and harder to move water up xylem less efficient @ top theoretically, limits growth to 122-130 m Drying soil adds opposite tension
Cohesion tension theory plants use water properties to cheat gravity Cohesion: H20 stick to other H20 molecules via H bonds Adhesion: water sticks to non-water molecules stick to sides of xylem tissues H20 not pulled straight up! Transpiration can pull water under tension
H2O also pulled in zig zag motion pits in xylem cells tracheids are twisted Vascular tissue is tough high resistance of lignified walls built not to collapse under tension Redwoods near theoretical limit!!!